Life history and environment in two species of intertidal barnacles.

Chthamalus anisopoma is common in the lower intertidal of the Gulf of California. It initiates breeding 6 wk after settlement: brooding and recruitment is year-round. Growth after settlement is rapid for 2 months, then slows markedly. Survivorship is fairly constant at all ages. Most mortality results from predatory gastropods, and from intraspecific crowding. Tetraclita stalactifera is generally confined to the upper intertidal. It failed to brood during the study period. The ovarian cycle indicates that brooding would otherwise take place during the summer. Age of first reproduction is c2yr. Recruitment of cyprids is strongly seasonal, peaking during August. Growth rate is relatively constant. Survivorship is initially very poor, apparently due to desiccation stress, but improves substantially after 4 months.-from Author